U.S. Pat. No. 3,826,737 discloses a conversion process using a moving bed catalyst, more particularly adapted to a co-current flow of the catalyst and the liquid charge, the latter being discharged at the reactor bottom through a cylindrical grid located at the bottom of a catalyst discharge cone supporting the catalyst bed.
Such a process has the disadvantage of a possible clogging of the grid by the catalyst particles pushed against said grid by the liquid charge discharged from the reactor bottom. This may then result in an irregular distribution of the fluids within the catalyst, flow difficulties for the catalyst bed with eventual blocking of certain zones thereof, together with an increase in catalyst attrition caused by friction between blocked particles and free particles of the catalyst bed and between free catalyst particles and the liquid charge discharge grid.
In order to avoid said disadvantages, U.S. Pat. No. 4,571,326 discloses two devices, illustrated in FIGS. 1 and 2 of the accompanying drawings, which do not conform with the invention. The disclosed technique involved injecting the liquid and the gases below the wall supporting the catalyst bed, while using a suitable device for the gas-liquid distribution.
More particularly, this result was obtained by a process (with progressive withdrawal of the powdery solid particles from a generally confined space) for introducing into said space a fluid charge formed of a liquid and a gas (generally hydrogen), said generally confined space having substantially the shape of an elongate and substantially vertical volume of revolution, the solid particles being introduced at the upper part and progressively withdrawn from the lower part of the enclosure after downward passage therethrough, whereas the fluid charge is introduced at least partly and generally continuously at the lower part of the enclosure and is withdrawn from the upper part thereof after upward passage through said enclosure. The solid particles are progressively withdrawn from the lower end of at least one flared zone, the shape of which depends on the reactor geometry and is generally that of an overturned cone or pyramid, i.e., a cone or pyramid whose apex is turned downwardly, said apex being pierced with a hole of suitable size for discharging the solid particles, the wall of said flared zone being substantially and regularly discontinuous, i.e., provided with at least several regularly spaced openings, each of sufficiently small size to avoid the passage of solid particles through said wall but sufficiently large to give passage to an upward flow of the fluid charge. The process is characterized by the introduction of the fluid charge at the lower part of said enclosure through at least one distribution zone of particular shape located below said wall.